1. Field of the Invention
The invention relates to protective devices for doorways and in particular, to an alarm which is mounted on the door adjacent the hinged edge, and which is actuated when the door is opened to sound an audible alarm. More particularly, the invention relates to a door alarm having a mechanical mechanism for actuating the alarm upon opening of the door and for maintaining the alarm actuated even if the intruder closes the door, and in which the alarm can be automatically armed by the user upon leaving the doorway.
2. Description of the Prior Art
Numerous devices have been devised and constructed over the years for mounting on a door or adjacent thereto for sounding an alarm when the door is opened to protect the occupants of the dwelling. Usually, these alarms are designed to be armed at night from within the protected dwelling and disarmed during the daytime when the door is continually being used. Examples of such prior art alarms are shown in U.S. Pat. Nos. 1,099,777, 1,377,939, 2,824,300, 3,121,864, 3,261,010, 3,270,333, 3,378,830, 3,768,086, 3,798,627, 3,878,539 and 4,059,832.
Many of these prior devices appear to provide a satisfactory alarm and are suitable for their intended purposes. However, nearly all of these known prior alarm devices, with the exception of the alarm shown in U.S. Pat. No. 3,121,864, are mounted closely adjacent the swinging end of the protected door or on the top thereof. This location enables the alarm to be deenergized quickly by an intruder when reaching only his hand and arm through a partially opened door. Also, some of the mounting brackets of these prior devices can be seen from the outside of the door revealing their presence to an intruder, and facilitating the disarming of them.
It also is desirable that such alarms remain activated even if the door is fully opened or immediately closed by an intruder. Many of the known prior alarm devices will deactivate immediately upon closing the door. U.S. Pat. No. 1,110,893 discloses a door knob mounted alarm which will remain activated until manually reset. However, many doors have door knobs or handles that prevent the mounting of such an alarm device thereon.
Another desirable feature not found in most prior alarm devices is means for arming the alarm by the user upon leaving the protected dwelling. U.S. Pat. No. 4,123,752 discloses the only alarm of which I am aware that permits the arming of an alarm upon the user leaving the doorway.
Also, it is desirable that these alarms are portable for use by an individual during travel, enabling the alarm to be mounted on the doorway of motels, hotels, etc., without requiring the use of attachment means such as screws or bolts which will mar the door or frame surface, as do most of the above-listed prior art alarms.
Although many of these prior art devices are believed to perform satisfactorily, I believe that my device provides an extremely simple, rugged and inexpensive alarm which provides the advantages of maintaining the alarm actuated even if the intruder immediately closes the door, provides an alarm which can be either permanently or temporarily installed on a doorway without marring the finish thereof, and provides an alarm which can be armed by the user upon leaving a protected dwelling by simple mechanical means.